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<h3>Notes:</h3><br>

<p><p style="direction:ltr;"><font color="#000000">The most common transport protocol is TCP, or transmission control protocol, which was developed in the early 70s. TCP provides reliable data streaming services in a unicast way. But here we are more interested in how TCP performs congestion control, in order to understand why it is not efficient in high bandwidth wide area networks.</font></p>
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<p style="direction:ltr;"><font color="#000000">TCP's congestion control mechanism is called AIMD, or additive increase multiplicative decrease, because it increases the congestion window size about one full-sized packet per RTT, and halves the size once a packet loss is detected.</font></p>
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<p style="direction:ltr;"><font color="#000000">Longer RTT means TCP needs a longer time to reach the maximum throughput, or the available network bandwidth. If there is a packet loss during this period, then TCP will never realize the optimal throughput.</font></p>
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<p style="direction:ltr;"><font color="#000000">Because TCP's performance relies on RTT, different concurrent flows with different RTTs will have different throughput. This is another problem of TCP, also known as RTT bias.</font></p>
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